The instant invention relates to wind energy conversion systems, specifically wind turbines.
The instant invention provides an omnidirectional, self-braking wind turbine. The wind turbine is suitable for a variety of built environment locations, such as airports and residential areas, as will become apparent in the description below.
Traditional horizontal axis wind turbines are mast mounted devices, which often interfere both aesthetically and physically with their surroundings. Their height both clutters the viewscape and makes them incompatible with the intended purpose of many of the windiest areas such as airports, metropolitan roof tops, and the shoreline.
Traditional wind turbines present a host of objections from neighbors. For example, traditional wind turbines cause shadow flicker as the blades rotate, falling ice when ice builds up on the blades and is then flung off, noise, and harm to wildlife. As a result, they are generally located away from populated areas where the power is needed, creating a power transport challenge, which limits the devices' effectiveness. Also, these objections pose significant challenges and delays during the permitting and approvals process, further complicating, and possibly preventing, the implementation of a wind energy project.
Traditional wind turbines are generally designed with large blades to intercept more wind and generate more power. This addition of moving mass increases their inefficiency because it requires more energy to get started, and aggravates many of the neighbor objections mentioned above. This additional size also complicates the mechanisms needed to control turbine speed and to brake the turbine in high winds.
Traditional horizontal axis wind turbines must be pointed into the wind. The increased size of traditional turbines makes the turbines less responsive to wind direction volatility. Even when the turbines are responsive to changes in wind direction, the mechanism to orient the turbines into the wind is complex, and is another source of failure.
Mast mounted devices require expensive site preparation and excavation, an expensive foundation, and heavy equipment. They are complicated and expensive to construct. Their geometry and complex mechanism create more opportunity for failure, increase both cost and downtime, and are challenging for technicians to access and maintain.
U.S. Pat. No. 8,459,930 discloses a vertical multi-phased wind turbine system. In particular, the vertical axis wind turbine uses an adjustable air scoop inlet section having variable geometry. The air scoop is adjustable so that it can be repositioned into the wind.
U.S. Pat. No. 8,534,992 to FloDesign Wind Turbine Corp. discloses a wind turbine that needs to be pointed into the wind. The geometry of the wind turbine limits the amount of wind that can be collected. This wind turbine is tower mounted and is incompatible with mounting on a building.
U.S. Pat. Nos. 8,257,020 and 7,315,093 teach wind turbine systems for buildings. According to these patents, the wind turbine system is placed at the edge of a building rooftop or built into the eaves, and is not suited for metropolitan or commercial applications, because the invention relies on a pitched roof to function, and commercial buildings have flat roofs. It is unidirectional, and it is size limited. The wind turbine system cannot be mounted at the center of a building, limiting its use and effectiveness.
U.S. Pat. No. 6,740,989 discloses an enclosed vertical axis wind turbine with focus on a turbulence causing flange on the leading edge of the stator and with a solid rotor. However, the shape of the rotor blades and the configuration of the chamber and enclosure face result in a significantly higher start up wind speed and inefficient use of the wind energy than the current state of the art.
U.S. Pat. No. 6,870,280 discloses an enclosed vertical axis wind turbine similar to McCamley in that the blades of the rotor do not touch and with curved stators and multiple levels. Because the invention relies on curved stators and an open rotor configuration and has a plurality of horizontal plates along its height, this invention has a higher start-up wind speed, is less efficient, is more difficult to brake and scale.
Similarly, Building Turbines, Inc. offers unidirectional turbines that must be at the edge of the building, limiting their use and effectiveness. The turbines blades are less durable because of the shape of their design and their fabric construction.
McCamley Middle East produces small scale wind turbines that are not self limiting, and do not have braking capabilities. The McCamley wind turbine is only 12 kW and is tower mounted. The design cannot be scaled to provide power to a large building. It has an upwind/downwind problem. It operates more like a vertical axis wind turbine than a backward curved impeller.
Other state of the art features bulbous and/or curved airfoil like stators which our research has demonstrated to hamper effectiveness. It features continuous, stationary stators which cannot adjust as wind speed and subsequent rotor rotation velocity increases, and thus hamper performance and is difficult to brake. It also features stators along the radial lines from the center of the rotor thus not optimizing direction and velocity of air injection into the chamber.
None of the prior art is able to start up at low wind speeds and reach full power at wind speeds as low as 15 mph. Nor can it be scaled to provide ample power for airports or other structures with populations having significant power demand (for example, in the range of 100 kW-200 kW).